Arrangements are known in the prior art of solid state color imaging apparatus using a single-chip solid state image pickup device having a plurality of photoelectric elements disposed in two-dimensional array together with a color filter having a specially disposed filter elements pattern, wherein the photoelectric elements are disposed shifted by a half pitch between n-th line and (n+1)-th line, and the disposition of the filter elements is shifted by 180.degree. of spatial phase of the filter element disposition, as shown in Japanese Patent Unexamined publication No. Sho 51-76015. The prior art is illustrated with reference to FIG. 1, which is a front view of a combined color filter and solid state image pickup device, wherein squares encircled by solid line designate color filter elements and smaller squares shown by dotted lines designate the photoelectric elements, and R, G and B show red filter, green filter and blue filter, respectively. This prior art intends to increase horizontal resolution by utilizing vertical correlation. Components of fundamental waves of signals in n-th horizontal line and (n+1)-th horizontal line obtained from the solid state image pickup device are shown in FIG. 2(a) and FIG. 2(b), respectively, wherein f.sub.s designates sampling frequency obtained from picture elements of the image sensor and is represented by the following equation: ##EQU1## where .tau..sub.H is the time period between the signals of the picture elements. In this diagram the parts shown by dotted lines represent components of a signal produced by modulation by reading-out by the photoelectric elements, i.e., folding components. Generally in an imaging apparatus, to obtain a signal of high resolution is one of the most important matters. For this purpose, the read-out signal from the photoelectric elements should be utilized to the highest frequency region. However, in the highest frequency parts of the read-out signal from the photoelectric elements, as shown in FIG. 2(a) and FIG. 2(b), the folding components, i.e. components produced by sampling with the photoelectric elements are enclosed. Therefore, when the highest frequency parts are used without removing the folding components, so-called folding distortion is produced thereby degenerating the picture quality. Furthermore, when a single-chip solid state imaging sensor is used to pick up a color picture signal, chrominance signals are spatially modulated and are superposed on the read-out signal from the photoelectric elements. Then a carrier of the chrominance signal is produced at a frequency which is a quotient of the sampling frequency by a number of picture elements included within one spatial period of the color filter elements. This induces picture distortion. For instance, when color filter elements repeat at the spatial period of three picture elements, then as shown in FIG. 2(a) and FIG. 2(b), a chrominance signal carrier is generated at the frequency of 1/3.multidot.f.sub.s, and its higher harmonic is generated at 2/3.multidot.f.sub.s.
In the above-mentioned prior art, in order to obtain picture quality of a small distortion and high resolution signal, it is necessary to isolate chrominance carrier components and folding components produced by sampling by the picture elements of the image sensor from the genuine picture signal component. And in this prior art, the folding components are removed by making the phases of these folding components of a line and a subsequent line to be opposite to each other and adding the opposite phase components with each other. Furthermore, by selecting color filter element disposition to be in opposite phase relation between a horizontal line and the subsequent horizontal line, the chrominance signal carrier produced at 1/3.multidot.f.sub.s is also eliminated as a result of the addition of a signal of a horizontal line and a signal of the subsequent horizontal line. In this way, in the prior art, the composed signal becomes as shown in FIG. 2(c), where only the fundamental frequency range component shown by the solid line and the chrominance signal carrier at 2/3.multidot.f.sub.s exist, enabling utilization of components of frequency range up to immediately lower 2/3.multidot.f.sub.s, thereby providing an imaging apparatus with reasonably small picture distortion.
However, in this prior art, the problem is that in order to assure the high resolution, an image projected on the photoelectric elements must have a vertical length over .tau..sub.v which is the vertical pitch of one horizontal line of scanning, thereby to give vertical correlation of the image. However, in an actual objective image, not all the image gives vertical correlation for more than .tau..sub.v in the vertical direction generally, and therefore the folding distortion induced by the sampling and the chrominance signal carrier at 1/3.multidot.f.sub.s cannot be sufficiently eliminated, thereby permitting introduction of picture distortion to some extent.
There has been another art which has not been published before the priority date of the present case and developed by the assignee corporation as described in the Japanese Patent Application No. Sho 56-24420. (Japanese Patent Unexamined Publication No. Sho 57-138281, published on Aug. 26, 1982. This is a basic application of the assignees prior U.S. Ser. No. 322,692, wherein horizontal dispositions of photoelectric elements between neighboring horizontal lines are shifted by .tau..sub.H /2, where .tau..sub.H is horizontal picture element pitch, and color filter elements are disposed in vertical stripes with 2/3.multidot..tau..sub.H pitch in horizontal direction as shown in FIG. 3.
In this second art, chrominance signals which are spatially modulated by a stripe color filter are further sampled by means of picture elements of the photoelectric elements, and the phase of sampling is shifted by 90.degree. (i.e. .tau..sub.H /2) between vertically neighboring horizontal lines, thereby producing a pair of different chrominance signals for even number horizontal lines and odd number horizontal lines, to be superposed on the luminance signal produced by the photoelectric elements. FIG. 4 shows the phase relation of chrominance signals which are sampled by picture element of the photoelectric elements and superposed on the luminance signal produced by the photoelectric elements. As shown in FIG. 4 the phase to be sampled by the picture elements of n-th horizontal line is in the same phase relation with that of the R component of the color filter, and the components R and G+B are superposed as the chrominance signal components on the luminance signal obtained from the photoelectric elements. In the next (n+1)-th horizontal line, G component and B component are superposed as the chrominance signal components. The feature of this prior art is that horizontal pitch of disposition of the color filter is selected to be 2/3 times the horizontal pitch .tau..sub.H of the picture elements of the photoelectric elements. And by shifting the horizontal disposition of the picture elements by 1/2.multidot..tau..sub.H at every line of horizontal scannings, the sampling phase at the time when an objective image which is spatially modulated by color filter is sampled by means of picture elements of the photoelectric elements, is changed. And thereby, chrominance signals are produced to be different from each other for odd number horizontal lines and even number horizontal lines, and the chrominance signals are to be superposed on the luminance signal obtained from the photoelectric elements. As a result of the above-mentioned structure, horizontal spatial relation between the picture elements and vertical stripe color filter elements can be further free. Further, vertical spatial relation between the filter and the picture elements are quite free since the color filter has a vertical stripe pattern. If the mutual horizontal relation between the color filter and the picture elements are shifted, the chrominance signals of respective horizontal scanning lines are sampled in a phase relation which is shifted by a phase angle corresponding to the spatial shift. Let us consider, for instance, an example where the color filter is horizontally shifted by 1/4.multidot..tau..sub.H from the spatial relation shown in FIG. 3, and this case is elucidated. FIG. 5 shows components of chrominance signals to be sampled by the picture elements when the color filter is shifted by 1/4.multidot..tau..sub. H. In FIG. 5, components projected on n-th horizontal line change from G+B of FIG. 4 showing the case of FIG. 3 to R+B component and G component. And components projected on (n+1)-th line are changed from the G component and B component of FIG. 4 to R+G component and B component of FIG. 5. As shown in the above-mentioned comparison, as a result of horizontal shifting of the mutual spatial relation of the color filter against the picture elements, effects of the shifting appears only on phase shift of the chrominance signal components. Accordingly, when demodulating the chrominance signal superposed on the luminance signal, desirable chrominance signals similar to those of ideal horizontal spatial relationship are obtainable, only by compensating the phase relation of the chrominance signals.
Though the above-mentioned assignee's prior art has a feature that horizontal spatial relation between the color filter and the picture elements may be not so severe, the problem is that the carrier frequency of the chrominance signals appears at 1/2.multidot.f.sub.s, for the f.sub.s sampling frequency of sampling by the picture elements. And since there is no appropriate method to eliminate this carrier signal of the chrominance signal, the luminance signal can be utilized only up to the frequency of 1/2.multidot.f.sub.s, and therefore a high resolution imaging apparatus is not obtainable.
A still other prior art has been described in the Japanese Examined Patent Publication No. Sho 55-24748. In this still other prior art, reading of the picture elements are made simultaneously for vertically neighboring two horizontal lines of picture elements as shown in FIG. 6. In this case, in one field of reading or scanning, all the horizontal lines of picture elements are scanned in combination of lines shown by n-th line, (n+1)-th line, (n+2)-th line . . . , thereby reading all the horizontal lines and in the next field of scanning, i.e., interlace scanning, combination of horizontal lines is changed to n'-th line, (n+1)'-th line . . . , thereby again reading all the horizontal lines in different combinations and thus making interlace scanning. This still other prior art has a feature that there is no need of using a delay circuit for delaying one horizontal line scanning time for preparing two color-difference signals hitherto used for such solid state image sensor. And further, since each picture element is read out twice in the time period for scanning one frame, time required for scanning one frame of picture is only the scanning time of one field. Therefore, the time period of storing the charge corresponding to the signal can be halved, and the problem of undesirable after-image in the reproduced picture can be solved. However, a measure to increase horizontal resolution of the picture for such assignees' prior art has not been described in the above-mentioned prior art.